refactor(datasource/npm): Convert to class (#14193)

lib/datasource/api.ts

lib/datasource/metadata.spec.ts

lib/datasource/npm/get.spec.ts

lib/datasource/npm/get.ts

lib/datasource/npm/index.spec.ts

lib/datasource/npm/index.ts

lib/datasource/npm/releases.ts

lib/manager/meteor/extract.ts

lib/manager/meteor/index.ts

lib/manager/npm/extract/index.ts

lib/manager/npm/index.ts

lib/manager/npm/post-update/index.ts

lib/manager/npm/post-update/yarn.ts

lib/workers/repository/init/vulnerability.ts

lib/workers/repository/process/lookup/index.spec.ts

lib/workers/repository/updates/generate.spec.ts